German Pat. OS 25 36 894 shows a mechanical steering mechanism in which a steering spindle rotates a helical pinion fixed thereon which engages a rack for transmitting mechanical power to a steering linkage. Owing to the resistance of the wheels on the roadway in the course of steering, the helical pinion on the steering spindle receives a reaction causing it to shift axially in one direction or the other depending upon direction of rotation of the steering spindle. Carried on the steering spindle is an inner valve sleeve having lands and grooves such that the reciprocal movement of the steering spindle effects relative shifting of the inner sleeve to control pressure and exhaust for a power steering servomotor.
The difficulty with the above described construction is due to the length of the housing of the mechanism which requires the valving to be at one end of the steering spindle, thus requiring an increased length of housing for the mechanism. Due to the confining nature of space in automotive vehicles, it is not possible to substitute the overly long construction of the prior art patent for a purely mechanical rack and pinion steering device.